The invention relates to a filter, especially for the filtration of the air intake of an internal combustion engine, consisting of an unfiltered air inlet, a housing, a filter insert disposed within the housing, and a clean air outlet.
A filter of this kind is disclosed, for example, in U.S. Pat. No. 4,929,263. In this filter a special housing is provided. This housing comprises a supporting body. The filter insert is contained in this supporting body. The supporting body is jacketed with the housing by the plastic blow molding process. The housing can be made with relatively thin walls. A disadvantage of this filter, however, is that it is not possible to replace the filter. At the regularly performed maintenance intervals the entire filter including the supporting body and the housing have to be replaced. Thus very high disposal costs are incurred and large quantities of unsorted waste is produced.
Published European Patent Application No. EP 524,333 discloses a method for producing a cast hollow body. This hollow body, which is also usable as a filter housing, is made by means of a hollow-forming core of nonmetallic material. The hollow-forming core is a thin-walled but already shaped core which can be stabilized against external casting pressure by an internal gas pressure. It is either lost or it can be removed from the cast hollow body after it has hardened, by melting or dissolving it out. This method enables complex cast hollow bodies to be produced, especially those designed for industrial use, such as bodies through which a gas is to flow. The method, however, is relatively complicated and thus it is not economical for filter housings such as those needed for the filtration of air aspirated into internal combustion engines.
Another disadvantage of the known systems or methods is that consideration is not given to various secondary factors, such as the noise emission properties of the filter housing, as well as the reduction of the orifice noise produced by the induction of the unfiltered air.